Twenty-eight new planets have been discovered outside the solar system in the past year, scientists announced yesterday.
The new discoveries raise the total number of exoplanets—worlds that circle other stars—to 236.
Many of the discoveries were published in scientific journals over the past year.
Monday's announcement at a meeting of the American Astronomical Society in Honolulu, Hawaii, was the first time the finds were presented together to the public.
Most of the new planets are probably huge balls of gas, more like Jupiter than Earth.
But scientists say the increasing rate at which they're finding new exoplanets makes it almost certain that the galaxy is swarming with smaller, rocky, and potentially habitable worlds that have so far eluded detection.
"We're finally now getting a sense that our solar system is not a rarity," said Geoff Marcy, who led the California and Carnegie Planet Search team that made many of the discoveries.
"There are indeed tens of billions of planetary systems out there, no doubt some of them rocky Earths, lukewarm, and suitable for life."
Marcy, an astrophysicist at the University of California, Berkeley, spoke to National Geographic News from the Keck Observatory atop Hawaii's Mauna Kea, where many of the new exoplanets were first spotted.
Because exoplanets are too far away to be seen directly, the 28 new planets were discovered by looking for the so-called Doppler wobble among stars.
This technique is based on the idea that if an unseen planet orbits a star, its gravitational pull causes a slight "wobble" in the light wavelengths coming from that star.
In addition to revealing the 28 new planets, advances in this technique recently allowed a postdoctoral astronomer at the University of Geneva in Switzerland to pin down the size of a large exoplanet that was discovered almost two years ago by Marcy's team.
Finding Other "Earths"
Based on data gathered so far, of the more than 200 billion stars in the Milky Way galaxy, at least 10 percent are thought to have planetary systems, UC Berkeley's Marcy said.
And at least 30 percent of all stars that are known to host planets have more than one, scientists say.
"Many of them remind us of our home solar system," Marcy said.
"We're finding a lot of cases in which the larger planets—the Jupiters and the Saturns—orbit further from the star than the smaller planets, and that is in fact the case for our solar system," he said.
Among this year's exoplanet finds are at least four new multiple-planet star systems.
Astronomers are finding that stars harboring the most planets are those that are rich in heavier elements, such as silicon, oxygen, iron, and nickel.
This may give researchers a clue as to where to look for possible habitable worlds.
"It's those richer stars that we're focusing our attention on, because those heavy elements are the building blocks of rocky planets like our Earth," Marcy said.
After all, he said, "it's not just the planets that require the heavy elements, it's the organisms themselves, should any exist."
There are bound to be TONS of potential new homes for us... we just have to know where to look.
Be sure to check out my previous post on the topic: A New Home?